KR100525708B1 - Pressurized light water reactor having bidirectional horizontal emergency core coolant splitter - Google Patents

Abstract

The present invention relates to a pressurized water reactor of the emergency core cooling water direct injection method, in order to ensure the safety of the reactor by reducing the emergency core cooling water injected in the event of a large cooling water loss due to cold tube break through the fracture surface, It is attached to the outer circumferential surface of the core barrel facing the emergency core coolant injection pipe, and a tangential vertical plate which divides the emergency core coolant water sprayed vertically from side to side to have a tangential velocity component, and the emergency core coolant Upper and lower baffles, upper and lower baffles, and upper and lower tangential vertical plates that block horizontal water drop and the water film from rising in the direction of gravity and increase horizontal velocity components. Emergency core cooling including auxiliary baffles located between the baffles to improve the uniformity of the horizontal velocity components Equipped with a two-way horizontal separator plate, the emergency core coolant is induced to the downstream area of the hot pipe with a relatively low steam velocity and low bypass rate, so that a large amount of emergency core coolant is applied to the core in the event of a large cold water loss caused by cold tube breakage. It provides a pressurized water reactor reactor that can be reached to reduce the maximum fuel cladding temperature and ensure safety by preventing reheating of the core.

Description

PRESSURIZED LIGHT WATER REACTOR HAVING BIDIRECTIONAL HORIZONTAL EMERGENCY CORE COOLANT SPLITTER}

The present invention relates to an emergency cooling system of a PWR reactor, and more particularly, to a cold leg in a PWR reactor in which emergency core cooling water is directly injected into the precipitation section of the reactor vessel. A large amount of coolant can be reduced by separating the emergency core coolant sprayed to hit the wall of the core barrel in both directions in the left and right directions to reduce the bypass discharge rate of the emergency core coolant through the accidental fracture surface. A pressurized water reactor reactor with an emergency core coolant bi-directional horizontal separator to reach the core.

As shown in FIG. 1, in general, the PWR reactor is composed of an external pressure vessel 5 and a core barrel 10 formed at a smaller diameter than the pressure vessel 5 and installed at the center of the pressure vessel. It comprises a reactor vessel (100). A core 7 into which a nuclear fuel rod is charged is located inside the core barrel 10, and the precipitation part 20, which is an annular space due to a diameter difference, between the core barrel 10 and the pressure vessel 5. Is formed. Then, the coolant is connected to the pressure vessel (5) is a plurality of low-temperature pipe 15 that is a circulation passage of the cooling water, and the coolant is introduced through the low-temperature pipe 15 and passed through the precipitation part 20 and the core (7) It consists of a configuration including a hot leg (Hot Leg) 25 is connected to the core barrel 10 to flow toward the steam generator.

Such reactors are pressurized water reactor reactors that operate as a high-energy nuclear fuel as an energy source.Therefore, there is a possibility that the accident can lead to a catastrophic disaster involving many casualties, from design to construction and operation. Every step must pass very strict safety standards.

As an example related to safety standards, the performance and safety verification of the reactor cooling system, which is conventionally employed in a PWR reactor, is performed during the design certification of the reactor and the reactor design and construction license examination by an institution such as the Korea Institute of Safety and Technology (KINS). Large Break Loss-of-Coolant Accident (LBLOCA) due to Double Ended Guillotine Break (LBLOCA), which has the highest fuel cladding temperature in the event of an accident, It is evaluated by standard. Here, the main evaluation criteria are whether the maximum fuel cladding temperature in the event of an accident is kept below the regulated value and whether the core is cooled.

In order to satisfy such a criterion, the PWR reactor is equipped with an emergency core coolant injection pipe (30) for injecting emergency core coolant, and the cold water (15) is broken and the coolant supplied through the cold pipe (15). It does not reach the core and prepares for accidents such as instantaneous breaks at both ends of the cold tube discharged out of the cooling system through the fracture surface (35).

As an example of the method of injecting the emergency core coolant, there is a method of injecting the emergency core coolant into the cold tube 15 (CLI: Cold Leg Injection). In this method, the emergency core cooling water injection pipe 30 is connected to the low temperature pipe 15, and thus, through the fracture surface 35 formed as the low temperature pipe 15 is completely cut at both ends in the instantaneous breakage of both ends of the low temperature pipe. All fluid flowing into the cold tube 15 is discharged out of the reactor cooling system. That is, the emergency core cooling water injected into the breaking low temperature pipe 15 does not contribute to the cooling of the core 7 at all, and there is a problem in that the emergency core coolant leakage loss discharged through the fracture surface 35 occurs.

As another example of the emergency core coolant injection method to improve the above problems, as shown in Figure 2, the method of directly injecting the emergency core coolant into the precipitation unit 20 of the reactor vessel (DVI: Direct Vessel Injection). That is, by injecting the emergency core coolant directly into the reactor vessel instead of the low temperature pipe 15, it is possible to reduce the outflow loss of the emergency core coolant that has been leaked out of the cooling system through the fracture surface 35 at the instantaneous fracture of the low temperature pipe. Referring to Korean Patent Publication No. 2001-76548, it will be described in more detail with respect to the pressurized water reactor reactor of the simple direct injection method as described above.

However, as shown in FIG. 3 and FIG. 4, the high velocity steam discharged from the precipitation section 20 between the pressure vessel 5 and the core barrel 10 to the fracture surface 35 of the low temperature pipe 15. A new problem arises, in which the proportion of emergency core cooling water drawn by bypass is increased. That is, in the low temperature pipe injection method, the cold emergency core cooling water is injected into the low temperature pipe 15 so that the amount of steam condensation is very large. However, in the method of directly injecting the reactor vessel 100, the low temperature pipe steam condensation hardly occurs. The vapor velocity of is much faster than in cold tube injection. Therefore, in the direct injection method, the emergency core coolant bypass discharge (ECC bypass) ratio, which is diverted to the fracture surface 35 by the emergency core cooling water by the high velocity steam in the precipitation section 20 of the reactor vessel 100, is increased. Engineering problems will arise.

If the emergency core coolant bypass ratio increases above a certain level, the maximum temperature of the fuel cladding increases during the Late Reflood Phase of LLBLOCA, and the core is reheated. Will cause serious problems. Therefore, in order for the core 7 to maintain a safer cooling state, the capacity of the pump mounted on the emergency core coolant injection pipe 30 is increased to increase the emergency core coolant injection flow rate or increase the emergency core coolant bypass discharge rate. Technical measures should be taken to reduce it. However, if the emergency core coolant bypass discharge rate cannot be reduced, the capacity of the emergency core coolant supply pump, which has been reduced by switching from the cold tube injection method (CLI) to the direct injection method (DVI), is increased again to increase the injection flow rate. This has to be done, resulting in economic losses due to the increase in pump capacity.

Conventionally, according to the experiments and calculations for the direct injection method (DVI), the ratio of emergency core coolant bypass discharge during instantaneous breakage failure at both ends of the cold tube is very large at the angle between the cold tube (15) and the emergency core coolant injection tube (30). By-passing of the emergency core coolant varies depending on the flow zones, such as the unbroken sound low temperature pipe 15 'and the low temperature break pipe 15 and the high temperature pipe 25, which are connected to the precipitation part 20. Appears.

As shown in FIGS. 3A and 4, in the flow region close to the break cold tube 15, the emergency core coolant is easily drawn to the break surface and discharged by the strong suction force of the flow sucked to the break surface, but the vapor velocity is relatively high. Emergency core coolant injected into a small area or the downstream flow zone behind the hot tube 25 (middle between 0 and 45 degrees between angles) does not draw well to the fracture surface but rather tends to penetrate below the precipitation section 20. Appears strong.

Nevertheless, in the conventional direct injection method, the flow characteristics of the precipitation part 20 of the reactor vessel 100 as described above are not saved at all. That is, by injecting the emergency core coolant simply into the region where the bypass phenomenon of the emergency core coolant is weak, it is simply injected directly to the emergency core coolant even near the fracture low temperature pipe 15 (45 degrees and 75 degrees section) where strong suction force is applied. Aqueous film A was formed and the bypass discharge rate increased. In addition, as shown in FIG. 3B, the water column (A) is radially spread by causing the water column sprayed through the emergency core cooling water injection pipe (30) to vertically hit the wall of the core barrel (10). The emergency core coolant spreading in the upper direction of the (20) loses kinetic energy while spreading in the opposite direction to gravity, and eventually the water film (A) becomes dry and escapes from the core barrel (10) wall and falls to the precipitation part. Liquid Drop) is created. As such, the droplets falling into the precipitation portion 20 are swept away by the strong steam flow of the precipitation portion 20 and are easily discharged to the fracture surface, thereby increasing the bypass ratio of the emergency core coolant.

By the above factors, although the conventional direct injection method is an alternative to the cold tube injection method, there was a problem that the bypass ratio of the emergency core cooling water was still large, and thus the high speed of the precipitation unit 20 was high. Mitigating the loss of emergency core coolant by reducing the percentage of emergency core coolant swept away by the emergency core coolant to the fracture surface (35) remains the biggest technical challenge.

In order to solve the problems of the prior art as described above,

An object of the present invention is to guide the emergency core cooling water directly injected into the reactor vessel to the hot tube downstream area to prevent the formation of the water film in the region adjacent to the low temperature pipe, and the water film is formed radially to escape the upper curl of the water film It prevents the formation of droplets according to the phenomenon, and reduces the ratio of emergency core coolant that is bypassed to the outside of the reactor cooling system through the breaking cold tube at the time of the instantaneous break in the cold tube and consequently the emergency core coolant delivered to the core through the precipitation part. In order to reduce the maximum temperature of the fuel cladding and prevent reheating of the core, it is possible to provide a pressurized water reactor reactor with an improved emergency core coolant direct injection method that can ensure the safety of the reactor.

The present invention for realizing this,

In a pressurized water reactor reactor in which emergency core cooling water is directly injected into the reactor vessel,

A plurality of emergency core coolant bidirectional horizontal separators, which are attached to the outer surface of the core barrel at a position opposite to each emergency core coolant injection pipe, each including a tangential vertical plate formed of two curved surfaces on the left and right of the vertical center line. It provides a pressurized water reactor reactor characterized in that it comprises a.

The emergency core coolant bidirectional horizontal separation plate includes a pair of upper and a pair of lower baffles extending horizontally toward the center of curvature at the upper and lower lines of each of the two curved surfaces forming the tangential vertical plate. It features.

The emergency core coolant bidirectional horizontal separator further includes at least one pair of auxiliary baffles extending in a curvature center side of each curved surface parallel to the upper and lower baffles at a position between the upper and lower baffles. It is done.

In addition, the pair of upper baffles and the pair of lower baffles are characterized in that the upper and lower plates are integrally formed to completely cover the upper or lower portion of the tangential vertical plate.

In addition, the upper plate and the lower plate is characterized in that it has a notch for preventing twisting rearward from each center.

BEST MODE Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the accompanying drawings. For reference, the same reference numerals will be given to the same components as in the prior art.

A pressurized water reactor reactor of the direct injection method according to the preferred embodiment of the present invention, as shown in Figure 6, a large tangential vertical plate 55, the upper plate 60 and the lower plate 65, and two pairs It is provided with a plurality of emergency core coolant bidirectional horizontal separation plate 50 made of a configuration including a secondary baffle (70).

Emergency core coolant bidirectional horizontal separator 50 is attached to the outer circumferential surface of the core barrel 10 at the position opposite to each emergency core coolant injection pipe 30, respectively, the emergency core coolant vertically incident toward the core barrel 10 The water column will be separated in both directions.

As shown in Figure 6 and 7, the tangential vertical plate 55 is formed as two curved surfaces of the left and right divided on the basis of the vertical center line located in the foremost state in the state attached to the core barrel 10, The curved surface is formed to have the same curvature, and is left-right symmetrical, as shown in Figure 7b, the center line of the left-right symmetric center line and the emergency core cooling water injection pipe 30 is aligned in a straight line, the tangential direction of the core barrel 10 The vertical velocity component of the emergency core coolant incident perpendicularly to is formed to have a sufficiently large curvature so as to be converted into a tangential velocity component by a gentle curve. Both left and right ends of the tangential vertical plate 55 are joined to the wall surface of the core barrel 10 by welding, and have a structure that can structurally withstand heat shrinkage and expansion. In addition, as shown in FIGS. 7A and 7C, the height of the tangential vertical plate 55 is an emergency core coolant in which the upper and lower ends of the tangential vertical plate 55 face each other in the state of being attached to the core barrel 10. Although higher than the upper end and lower than the lower end of the injection tube 30, in consideration of the effect of gravity, it is preferable to make the difference of the lower side larger.

The upper plate 60 and the lower plate 65 are formed in the same shape, and are combined to cover the upper and lower portions of the tangential vertical plate 55, respectively. The upper plate 60 and the lower plate 65 are each formed in the form of a single plate, but two curved surfaces of the tangential vertical plate 55 protruding forward from the upper and lower lines of the tangential vertical plate 55. Each top line and bottom line is formed in a form including a baffle (Baffle) corresponding to a portion extending horizontally toward the curvature center side. In other words, to prevent the incident water column from spreading to the upper and lower portions, the upper plate 60 formed of a single plate is formed in a shape including a pair of upper and lower upper baffles 80, and a lower plate also formed of a single plate ( 65 is also formed in the form including a pair of left and right lower baffles (90).

In addition, the upper plate 60 and the lower plate 65 are formed with notches 61 and 66 for preventing warpage that are rearwardly formed at their respective centers, and thus the tangential vertical plate 55 and the core barrel 10 are formed. The fluid is freely allowed to enter and exit the vertical space surrounded by the space, thereby preventing problems such as steam expansion in the local space, resulting in structural instability. At the same time, a margin for thermal contraction or thermal expansion is secured by the width of the notches 61 and 66, thereby preventing warping.

The auxiliary baffle 70 is additionally attached to effectively guide the flow path of the water column incident by assisting the upper baffle 80 and the lower baffle 90 included in the upper plate 60 and the lower plate 65. It is coupled to the tangential vertical plate 55 in a form extending from the position between the 80 and the lower baffle 90 to the curvature center side of each curved parallel to the upper baffle 80 and the lower baffle 90. In addition, referring to FIG. 6, a total of two pairs of auxiliary baffles 70 are coupled between the upper baffle 80 and the lower baffle 90, but the number thereof may be changed.

The upper and lower baffles 80, 90 and the auxiliary baffle 70 are similar in shape, but serve to play a main role in blocking the water film formed by the incident water column from spreading up and down and dividing horizontally. It is preferable that the upper and lower baffles 80 and 90 are formed to have a wider width than the auxiliary baffle 70. In addition, the auxiliary baffle 70 serves to make the horizontal velocity of the water column sprayed from the emergency core cooling water injection pipe 30 bilaterally divided between the upper and lower baffles 80 and 90. At the same time, it also serves as a reinforcement for structurally supporting the tangential vertical plate 55.

Hereinafter, the flow of coolant in a PWR reactor having an emergency core coolant bidirectional horizontal separator according to the present invention will be described.

First, the emergency core cooling water injected by the direct injection method through the emergency cooling water injection pipe 30 due to the instantaneous breakage accident at both ends of the low temperature pipe is applied to the core barrel 10 facing the outlet of the emergency cooling water injection pipe 30. The emergency core coolant bidirectional horizontal separator 50 is attached to the left and right directions. That is, the vertical velocity component of the emergency core coolant is converted into the tangential velocity component along the gentle curved surface of the tangential vertical plate 55 to spread from side to side.

In more detail, in the direct injection method according to the prior art, the water film sprayed from the emergency core coolant injection pipe 30 hits the core barrel 10 wall and spreads radially and draws a vertical downward parabola (see FIG. 5). The core coolant is guided in both directions by the bidirectional horizontal separator 50 to convert the core barrel wall into a horizontal water film B in a horizontal and lateral tangential direction (see FIGS. 6, 8, and 9). .

As described above, the emergency core coolant is separated in both horizontal and horizontal directions by the tangential vertical plate 55, and then induced to form a water film in the horizontal direction according to the linear kinetic energy, and then lowered by gravity to break the cold tube 15. The water film formed near) is induced near the hot tube. That is, if the induction of the emergency core coolant water film formation into the downstream region of the hot tube where the infiltration tendency of the lower portion 20 of the emergency core coolant is very large, it does not contribute to the cooling of the core and bypasses the fracture surface of the broken cold tube 15. The rate of emergency core coolant discharged is greatly reduced.

In other words, as shown in FIG. 10, the water film formed in a simple vertical shape at the time of the direct injection type emergency core cooling water injection according to the prior art is converted into a horizontal water film (B), whereby A large amount of emergency core coolant is induced into the hot tube downstream region (near 0 degrees), which is located at a long distance and has strong detour emission reduction characteristics, and thus, the flow rate to the surrounding region of the broken cold tube 15 decreases relatively. When the cold tube breaks, the rate of bypass discharge of the emergency core coolant drawn to the fracture surface by the high-speed steam is reduced, so that a large amount of emergency core coolant reaches the core 7 through the lower part of the precipitation part.

In the formation of the flow as described above, the upper baffle 80 included in the upper plate 60 blocks the upper expansion of the water film against the gravity in the conventional radial water film to prevent kinetic energy to dry up and prevent the falling off of the film It blocks the cause phenomenon of droplet generation.

In addition, the lower baffle 90 included in the lower plate 65 blocks the water film extending downward when the incident emergency core coolant water column vertically hits the wall of the core barrel 10 and then collides with the core barrel in the downward direction. It will act to block the formation of meninges. Accordingly, the horizontal velocity component of the flow is increased by blocking the flow descending in the direction of gravity to induce the flow further to the region farther from the break cold tube 15, thereby contributing to reducing the emergency core coolant bypass discharge rate.

In addition, the auxiliary baffle 70 serves to further reinforce the horizontal velocity component of the incident emergency core coolant to spread more evenly from side to side.

In summary, the emergency core injection water injected into the core barrel 10 vertically during the direct injection of the emergency core coolant is basically formed in the horizontal and lateral tangential directions of the core barrel 10 through the tangential vertical plate 55. By changing the direction smoothly, by blocking the water film spreading up and down at the injection point by the upper and lower baffles (80) and the lower baffles (90) located in the top and bottom to increase the horizontal velocity component and prevent the formation of droplets, The baffle 70 is used to further increase the horizontal speed, but also to increase the uniformity of flow in the horizontal speed direction, thereby forming an effective horizontal water film.

Accordingly, the present invention allows the horizontal water film to be spread from side to side instead of the radial water film, which was a problem of the emergency core coolant direct injection method according to the prior art, and the emergency core coolant is easily bypassed by the strong suction force of the broken cold tube. The emergency core cooling water injected into the hot water zone is led to the hot tube downstream area, which has a low tendency to bypass.

As a result, the loss of momentum caused by the impingement of the emergency core coolant perpendicularly to the core barrel wall is reduced, and the vapor velocity of the water film formed in the cold low-temperature tube area when the radial water film is formed is easily discharged to the fracture surface. It is possible to reduce the bypass ratio of emergency core coolant by leading to a relatively small hot tube wake region.

By providing a pressurized water reactor reactor equipped with an emergency core coolant bidirectional horizontal separator according to the present invention as described above, it is possible to suppress the increase of the maximum fuel cladding temperature, which is the main concern of safety regulators in the event of a large coolant loss caused by cold tube breakage, and later. It will prevent the reheating of the core during the re-watering period to solve the thermal and hydraulic safety problems of the reactor, and at the same time reduce the capacity of the emergency core coolant injection pump, which inevitably increases the capacity as the emergency core coolant bypass ratio increases. The economic benefits can be achieved.

While the invention has been shown and described in connection with specific embodiments, it is conventional in the art that various changes, modifications and variations are possible without departing from the spirit and scope of the invention as indicated by the appended claims. Anyone with knowledge of this will easily know.

1 is a conceptual diagram schematically showing a planar cross-section and a longitudinal cross-sectional structure of a pressurized water reactor reactor of the emergency core cooling water low temperature pipe injection method according to the prior art,

2 is a conceptual view schematically showing a planar cross section and a longitudinal cross-sectional structure of a pressurized water reactor reactor according to the prior art;

3 is a view showing the flow of emergency core cooling water formed in the direct injection type PWR reactor of FIG.

3A is a conceptual diagram illustrating the water film form of the emergency core coolant formed on the outer circumferential surface of the core barrel from the front;

3B is a conceptual view illustrating a water film type of emergency core coolant from an angle different from that of FIG. 3A;

FIG. 4 is a diagram illustrating a superimposition of the emergency core coolant water film form and the precipitation part flow characteristics in the form of an expanded form around the fracture cold tube of the direct injection type PWR reactor of FIG. 2;

5 is a conceptual view showing the water film spreading direction of the emergency core cooling water in the direct injection type PWR reactor of FIG.

6 is a view showing the structure of the emergency core cooling water bi-directional horizontal separation plate according to an embodiment of the present invention,

6a is an exploded perspective view,

6b is an assembled and attached perspective view;

7 is a view illustrating the emergency core coolant bidirectional horizontal separator of FIG. 6 in various directions;

7A is a front view,

7B is a plan view,

7C is a side view,

8 is a conceptual diagram showing the water film spreading direction of the emergency core coolant in the PWR reactor having the same type of emergency core coolant bidirectional horizontal separator according to the present invention.

9 is a conceptual view showing the water film form of the emergency core cooling water formed in the direct injection type PWR reactor according to the present invention;

10 is a diagram showing the superimposition of the emergency core coolant water film form and the precipitation part flow characteristics in the vicinity of the fracture cold tube of the direct injection type PWR reactor according to the present invention in an expanded form.

* Description of the symbols for the main parts of the drawings *

5: pressure vessel 7: core

10: core barrel 15: low temperature tube

20: precipitation part 25: high temperature tube

30: Emergency core coolant injection pipe

50: emergency core coolant bidirectional horizontal separator

55: tangential vertical plate 60: top plate

61, 66: notch 65: bottom plate

70: auxiliary baffle 80: upper baffle

90: lower baffle 100: reactor vessel

Claims (5)

In a pressurized water reactor reactor in which emergency core cooling water is directly injected into the reactor vessel, A plurality of emergency core coolant bidirectional horizontal separators, which are attached to the outer surface of the core barrel at a position opposite to each emergency core coolant injection pipe, each including a tangential vertical plate formed of two curved surfaces on the left and right of the vertical center line. Pressurized water reactor reactor characterized in that it comprises a. The method of claim 1, The emergency core coolant bidirectional horizontal separation plate includes a pair of upper and a pair of lower baffles extending horizontally toward the center of curvature at the upper and lower lines of each of the two curved surfaces forming the tangential vertical plate. Pressurized water reactor reactor characterized in that. The method of claim 1, The emergency core coolant bidirectional horizontal separation plate further includes a pair of at least one auxiliary baffle extending in a curvature center side of each curved surface parallel to the upper and lower baffles at a position between the upper and lower baffles. Pressurized water reactor. The method of claim 2 or 3, The pair of upper baffles and the pair of lower baffles are respectively provided as an upper and lower plates integrally formed to completely cover the upper or lower portion of the tangential vertical plate. The method of claim 4, wherein The upper and lower plates are pressurized water reactor reactor characterized in that it has a notch for preventing warping in the rear at each center.